lib/Target/XCore/XCoreLowerThreadLocal.cpp

   1 //===-- XCoreLowerThreadLocal - Lower thread local variables --------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 ///
  10 /// \file
  11 /// This file contains a pass that lowers thread local variables on the
  12 ///        XCore.
  13 ///
  14 //===----------------------------------------------------------------------===//
  15
  16 #include "XCore.h"
  17 #include "llvm/IR/Constants.h"
  18 #include "llvm/IR/DerivedTypes.h"
  19 #include "llvm/IR/GlobalVariable.h"
  20 #include "llvm/IR/IRBuilder.h"
  21 #include "llvm/IR/Intrinsics.h"
  22 #include "llvm/IR/Module.h"
  23 #include "llvm/IR/NoFolder.h"
  24 #include "llvm/IR/ValueHandle.h"
  25 #include "llvm/Pass.h"
  26 #include "llvm/Support/CommandLine.h"
  27 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  28
  29 #define DEBUG_TYPE "xcore-lower-thread-local"
  30
  31 using namespace llvm;
  32
  33 static cl::opt<unsigned> MaxThreads(
  34   "xcore-max-threads", cl::Optional,
  35   cl::desc("Maximum number of threads (for emulation thread-local storage)"),
  36   cl::Hidden, cl::value_desc("number"), cl::init(8));
  37
  38 namespace {
  39   /// Lowers thread local variables on the XCore. Each thread local variable is
  40   /// expanded to an array of n elements indexed by the thread ID where n is the
  41   /// fixed number hardware threads supported by the device.
  42   struct XCoreLowerThreadLocal : public ModulePass {
  43     static char ID;
  44
  45     XCoreLowerThreadLocal() : ModulePass(ID) {
  46       initializeXCoreLowerThreadLocalPass(*PassRegistry::getPassRegistry());
  47     }
  48
  49     bool lowerGlobal(GlobalVariable *GV);
  50
  51     bool runOnModule(Module &M) override;
  52   };
  53 }
  54
  55 char XCoreLowerThreadLocal::ID = 0;
  56
  57 INITIALIZE_PASS(XCoreLowerThreadLocal, "xcore-lower-thread-local",
  58                 "Lower thread local variables", false, false)
  59
  60 ModulePass *llvm::createXCoreLowerThreadLocalPass() {
  61   return new XCoreLowerThreadLocal();
  62 }
  63
  64 static ArrayType *createLoweredType(Type *OriginalType) {
  65   return ArrayType::get(OriginalType, MaxThreads);
  66 }
  67
  68 static Constant *
  69 createLoweredInitializer(ArrayType *NewType, Constant *OriginalInitializer) {
  70   SmallVector<Constant *, 8> Elements(MaxThreads);
  71   for (unsigned i = 0; i != MaxThreads; ++i) {
  72     Elements[i] = OriginalInitializer;
  73   }
  74   return ConstantArray::get(NewType, Elements);
  75 }
  76
  77 static Instruction *
  78 createReplacementInstr(ConstantExpr *CE, Instruction *Instr) {
  79   IRBuilder<NoFolder> Builder(Instr);
  80   unsigned OpCode = CE->getOpcode();
  81   switch (OpCode) {
  82     case Instruction::GetElementPtr: {
  83       SmallVector<Value *,4> CEOpVec(CE->op_begin(), CE->op_end());
  84       ArrayRef<Value *> CEOps(CEOpVec);
  85       return dyn_cast<Instruction>(Builder.CreateInBoundsGEP(
  86           cast<GEPOperator>(CE)->getSourceElementType(), CEOps[0],
  87           CEOps.slice(1)));
  88     }
  89     case Instruction::Add:
  90     case Instruction::Sub:
  91     case Instruction::Mul:
  92     case Instruction::UDiv:
  93     case Instruction::SDiv:
  94     case Instruction::FDiv:
  95     case Instruction::URem:
  96     case Instruction::SRem:
  97     case Instruction::FRem:
  98     case Instruction::Shl:
  99     case Instruction::LShr:
 100     case Instruction::AShr:
 101     case Instruction::And:
 102     case Instruction::Or:
 103     case Instruction::Xor:
 104       return dyn_cast<Instruction>(
 105                   Builder.CreateBinOp((Instruction::BinaryOps)OpCode,
 106                                       CE->getOperand(0), CE->getOperand(1),
 107                                       CE->getName()));
 108     case Instruction::Trunc:
 109     case Instruction::ZExt:
 110     case Instruction::SExt:
 111     case Instruction::FPToUI:
 112     case Instruction::FPToSI:
 113     case Instruction::UIToFP:
 114     case Instruction::SIToFP:
 115     case Instruction::FPTrunc:
 116     case Instruction::FPExt:
 117     case Instruction::PtrToInt:
 118     case Instruction::IntToPtr:
 119     case Instruction::BitCast:
 120       return dyn_cast<Instruction>(
 121                   Builder.CreateCast((Instruction::CastOps)OpCode,
 122                                      CE->getOperand(0), CE->getType(),
 123                                      CE->getName()));
 124     default:
 125       llvm_unreachable("Unhandled constant expression!\n");
 126   }
 127 }
 128
 129 static bool replaceConstantExprOp(ConstantExpr *CE, Pass *P) {
 130   do {
 131     SmallVector<WeakTrackingVH, 8> WUsers(CE->user_begin(), CE->user_end());
 132     llvm::sort(WUsers.begin(), WUsers.end());
 133     WUsers.erase(std::unique(WUsers.begin(), WUsers.end()), WUsers.end());
 134     while (!WUsers.empty())
 135       if (WeakTrackingVH WU = WUsers.pop_back_val()) {
 136         if (PHINode *PN = dyn_cast<PHINode>(WU)) {
 137           for (int I = 0, E = PN->getNumIncomingValues(); I < E; ++I)
 138             if (PN->getIncomingValue(I) == CE) {
 139               BasicBlock *PredBB = PN->getIncomingBlock(I);
 140               if (PredBB->getTerminator()->getNumSuccessors() > 1)
 141                 PredBB = SplitEdge(PredBB, PN->getParent());
 142               Instruction *InsertPos = PredBB->getTerminator();
 143               Instruction *NewInst = createReplacementInstr(CE, InsertPos);
 144               PN->setOperand(I, NewInst);
 145             }
 146         } else if (Instruction *Instr = dyn_cast<Instruction>(WU)) {
 147           Instruction *NewInst = createReplacementInstr(CE, Instr);
 148           Instr->replaceUsesOfWith(CE, NewInst);
 149         } else {
 150           ConstantExpr *CExpr = dyn_cast<ConstantExpr>(WU);
 151           if (!CExpr || !replaceConstantExprOp(CExpr, P))
 152             return false;
 153         }
 154       }
 155   } while (CE->hasNUsesOrMore(1)); // We need to check because a recursive
 156   // sibling may have used 'CE' when createReplacementInstr was called.
 157   CE->destroyConstant();
 158   return true;
 159 }
 160
 161 static bool rewriteNonInstructionUses(GlobalVariable *GV, Pass *P) {
 162   SmallVector<WeakTrackingVH, 8> WUsers;
 163   for (User *U : GV->users())
 164     if (!isa<Instruction>(U))
 165       WUsers.push_back(WeakTrackingVH(U));
 166   while (!WUsers.empty())
 167     if (WeakTrackingVH WU = WUsers.pop_back_val()) {
 168       ConstantExpr *CE = dyn_cast<ConstantExpr>(WU);
 169       if (!CE || !replaceConstantExprOp(CE, P))
 170         return false;
 171     }
 172   return true;
 173 }
 174
 175 static bool isZeroLengthArray(Type *Ty) {
 176   ArrayType *AT = dyn_cast<ArrayType>(Ty);
 177   return AT && (AT->getNumElements() == 0);
 178 }
 179
 180 bool XCoreLowerThreadLocal::lowerGlobal(GlobalVariable *GV) {
 181   Module *M = GV->getParent();
 182   if (!GV->isThreadLocal())
 183     return false;
 184
 185   // Skip globals that we can't lower and leave it for the backend to error.
 186   if (!rewriteNonInstructionUses(GV, this) ||
 187       !GV->getType()->isSized() || isZeroLengthArray(GV->getType()))
 188     return false;
 189
 190   // Create replacement global.
 191   ArrayType *NewType = createLoweredType(GV->getValueType());
 192   Constant *NewInitializer = nullptr;
 193   if (GV->hasInitializer())
 194     NewInitializer = createLoweredInitializer(NewType,
 195                                               GV->getInitializer());
 196   GlobalVariable *NewGV =
 197     new GlobalVariable(*M, NewType, GV->isConstant(), GV->getLinkage(),
 198                        NewInitializer, "", nullptr,
 199                        GlobalVariable::NotThreadLocal,
 200                        GV->getType()->getAddressSpace(),
 201                        GV->isExternallyInitialized());
 202
 203   // Update uses.
 204   SmallVector<User *, 16> Users(GV->user_begin(), GV->user_end());
 205   for (unsigned I = 0, E = Users.size(); I != E; ++I) {
 206     User *U = Users[I];
 207     Instruction *Inst = cast<Instruction>(U);
 208     IRBuilder<> Builder(Inst);
 209     Function *GetID = Intrinsic::getDeclaration(GV->getParent(),
 210                                                 Intrinsic::xcore_getid);
 211     Value *ThreadID = Builder.CreateCall(GetID, {});
 212     Value *Addr = Builder.CreateInBoundsGEP(NewGV->getValueType(), NewGV,
 213                                             {Builder.getInt64(0), ThreadID});
 214     U->replaceUsesOfWith(GV, Addr);
 215   }
 216
 217   // Remove old global.
 218   NewGV->takeName(GV);
 219   GV->eraseFromParent();
 220   return true;
 221 }
 222
 223 bool XCoreLowerThreadLocal::runOnModule(Module &M) {
 224   // Find thread local globals.
 225   bool MadeChange = false;
 226   SmallVector<GlobalVariable *, 16> ThreadLocalGlobals;
 227   for (GlobalVariable &GV : M.globals())
 228     if (GV.isThreadLocal())
 229       ThreadLocalGlobals.push_back(&GV);
 230   for (unsigned I = 0, E = ThreadLocalGlobals.size(); I != E; ++I) {
 231     MadeChange |= lowerGlobal(ThreadLocalGlobals[I]);
 232   }
 233   return MadeChange;
 234 }